Poxviruses, long thought to replicate exclusively in the cytoplasm of infected cells, have now been shown to require some nuclear function for maturation. This project is concerned with the role of the nucleus in poxvirus replication and the role of the virus in the transient hyperplastic response. The avian poxviruses, fowlpox and juncopox, will be utilized since their extended growth cycle and marked hyperplastic response offer certain advantages. Viral-specific RNA and DNA from nuclei of infected cells will be characterized with respect to size and genomic complexity. Viral nucleic acid synthesis in nuclei from infected cells will be analyzed and kinetics of synthesis measured. The avian poxvirus genomes will be compared with the vaccinia genome by restriction endonuclease digestion and DNA-DNA reassociation kinetics to determine the degree of homology and differences in the molecules. Infected tissue will be examined to more clearly define the hyperplastic response produced by poxviruses. A search for viral-specific macromolecules in hyperplastic tissue will also be undertaken. These studies, along with characterization of nucleic acid metabolism in infected cells and comparison of vaccinia and avian poxvirus genomes, may elucidate some control mechanisms of a benign hyperplastic response.